1. Technical Field
The present invention relates to a double-side recording apparatus including an inversion unit which inverts the recording face of a recording medium from a front side to a back side in order to perform the double-side recording of the recording medium, and a medium transporting method in the double-side recording apparatus.
2. Related Art
In the past, as one kind of a double-side recording apparatus, a double-side printing apparatus has been known (for example, JP-A-2004-314505, JP-A-2006-188068, etc.). Such a kind of double-side printing apparatus is provided with an inversion unit which inverts the paper after the printing of a front side. Thus, after the ending of the printing of the front side (first face) of the paper, the paper is inverted by the inversion unit such that the back side (second face) of the paper becomes the face to be recorded.
Incidentally, an ink jet type recording apparatus is provided with a maintenance device which prevents/restores so that there is no clogging due to the thickening in viscosity of ink in the nozzles of the recording head (for example, JP-A-2005-144690, JP-A-10-202904, JP-A-2005-125759, etc.). The maintenance device is provided with a cap, and at the time of waiting when printing is not carried out, the recording head moves to a home position located at the end of a moving path, which is deviated from a printing area, and in this state, the cap of maintenance device ascends, so that the recording head waits while capped.
Further, a maintenance device is also known which is provided with a locking member (locking lever) which regulates the position of a carriage at a home position (cleaning position) so that the capping can be carried out in a state in which the recording head has been disposed at the home position (for example, JP-A-10-202904 and JP-A-2005-125759). In this maintenance device, the cap, a wiper, and the locking lever are driven through the same power transmission mechanism.
For example, in JP-A-2005-144690, an ink jet printer is disclosed in which a paper feed motor (PF motor) driving a transporting roller is used as a rotation driving source common to a wiper, a cap, and a suction pump, which constitute a maintenance device (maintenance mechanism). In this printer, the paper feed motor is driven to rotate normally when driving a paper feeding roller and the transporting roller, and driven to rotate in reverse when operating the wiper, the cap, and the suction pump.
Further, a scanner-equipped printer is also known which is provided with a scanner reading a manuscript and a copy function which can print at a printer section by converting the image data read by the scanner to printing data by internal image processing (for example, JP-A-2007-295348 and JP-A-2005-111668).
For example, in the case of performing automatic double-side printing by the scanner-equipped printer, printing is started after the reading of a manuscript for front side printing by the scanner, so that there is a case where an interval is generated until, in order that a manuscript for back side printing be read, a user looks for the page of a book, selects a manuscript among plural pieces, or inverts and sets a manuscript. Further, also after a manuscript for back side printing has been read by the scanner, an image process which converts the image data (RGB image data) of, for example, a RBG color system read by the scanner to the image data (printing data) of a CMYK color system is performed, so that there was a case where a relatively long waiting time is generated after the front side printing ends and before the data for the back side printing are generated.
If such a waiting time is generated, in order to prevent the thickening in viscosity of ink in the nozzles, the cap and the locking member ascend, so that the recording head is capped. For example, in the case of performing one side printing, when a waiting time is generated after the end of the printing until the instructions for the next page printing are given, the capping or the carriage locking is performed, and at that time, since the paper after the end of the printing is already being discharged, even if the transporting roller is rotationally driven at the time of the ascending of the cap or the locking member, no problems arise.
However, in the case of an automatic double-side printing, waiting is done in a state in which the paper after the front side printing ending remains nipped by at least one of the transporting roller and the paper discharging roller (transportation system rollers) without being discharged, until the instructions for back side printing are given. For this reason, if the PF motor is driven for the capping and the carriage locking during the waiting, the transportation system rollers using a common power source are rotated together, so that the problem of the deviation of the paper position arises.
For example, in a case where the driving direction of the PF motor in the capping and the carriage locking is the same as the forward-feed direction of the paper, the paper is shifted to the downstream side of the transportation direction, and in this case, a state in which the paper has come out further than necessary on a paper discharging stacker during the waiting occurs, and therefore, there is a danger that, for example, a problem that the user draws out the paper by mistake can arise. On the other hand, in a case where the driving direction of the PF motor in the capping and the carriage locking is the same as the reverse-feed direction of the paper, the paper is shifted to the upstream side of the transportation direction, and in this case, the paper after the front side printing is held for a long time at the upstream side position which is not supposed to happen, and thus the upstream side end of the paper touches, for example, the upstream side parts or the inner wall in the paper transportation path, so that an excess load is applied to the paper or the paper is held with the printed face thereof touching the inner wall, whereby printing defects can be caused.
Further, there is a problem that the paper becomes shifted after the front side printing because the PF motor is also driven in a case where another mechanism driven using the PF motor as a common power source is driven, as in the case at the time of cleaning, so that cleaning is performed. For example, in a case where another sequence is started during a printing sequence, in the printing sequence, the deviation of the paper position due to the rotational driving of the motor by another sequence cannot be caught, and therefore in a case where the position of the paper has become deviated due to the driving of another sequence, the back side printing is started as it is. In this case, a problem that the paper inversion operation cannot be correctly performed due to the position deviation of the paper arises. This necessitates switching the transportation system rollers from the reverse-rotation to the normal-rotation at the interval after the nipping of the tail end of the paper was released from the transportation system rollers by driving the PF motor in the direction of transporting the paper to the upstream side by the reverse driving of the transporting roller until the leading end of the paper inverted at the inversion unit is nipped again by the transportation system rollers. The timing of switching the driving direction of the PF motor is managed by a step number which drives the PF motor from the position at the time of the end of the front side printing of the paper. For example, if the position of the paper is deviated, the PF motor is switched at the timing driven with a step number from the deviated position, and therefore, for example, at a step in which the tail end in the inversion direction of the paper is still nipped by the transportation system rollers, or a step in which the leading end in the inversion direction of the paper has already reached the transportation system rollers, the driving direction of the PF motor 39 is switched at an inappropriate timing, so that a problem such as the occurrence of, for example, an inversion error arises.